The present invention relates generally to padded elements and specifically to motor vehicle seats, and is particularly concerned with a method for the manufacture of cushions for such seats, wherein a cover is applied to a padding having shaped surface and formed into a configuration complementary to the shaped surface of the padding.
In the present description and in the claims which follow, the term "cushion" refers to the part of the seat constituting the seat squab or even the backrest and formed from padding (for example of expanded plastics material) provided with a cover (of cloth, leather, synthetic material or the like) possibly provided on its inside with a relatively thin, soft layer of expanded plastics material.
According to one known technique, the cushion is produced by providing padding of expanded plastics material and covering this padding with cloth on the upper surface of the cushion and on a perimetral strip arranged at the front and on the two sides of the cushion. The cloth cover is fixed to the padding with adhesive material or with fixing elements which attach the cloth to the body of expanded plastics material.
Compared to more conventional techniques in which the cloth cover is attached to the body of expanded plastics material by means of sewing, the above known technique has the advantage of being more suitable for mass production and, in particular, of allowing the manufacturing process to be automated, whilst still enabling the production of anatomically complex shapes in accordance with the requirements of ergonomics and comfort. On the other hand, this known method involves the risk that, as a result of the attachment of the cloth cover to the anatomical upper surface of the padding, tears may form in the cloth since it is not elastic.
In order to solve this problem, the use of a thermoformable material has been suggested for covering the padding of expanded plastics material. This material is first heated and then formed into the required shape by means of cold pressing in a die. The material thus shaped is then attached to the body of expanded plastics material. This known method, however, has the disadvantage of requiring the use of a thermoformable material, which is relatively expensive, and of not permitting the use of materials bearing decorative designs, as the designs are deformed during the thermoforming operation.
A solution to the problem of producing a cushion with a complex anatomical shape, using a normal non-elastic material for the cover but nevertheless avoiding the risk of splitting and/or tearing of the material during its attachment to the stuffing, consists of forming the covering material before its application to the padding by means of a hot pressing operation with the application of steam. A method of this type is described and illustrated in the documents FR-A-No.2 347 306. Although, on the one hand, the simple idea of giving a non-elastic material a certain shape by means of hot pressing in the presence of steam certainly constitutes an obvious step for an expert in the art of forming materials, in view of the fact that it is the conventional method used, even in the home, for shaping articles of clothing as well as covering materials in general, it should be appreciated, on the other hand, that the practical application of this idea on an industrial scale is not at all immediate. In fact, experiments conducted by the Applicant have shown that the method mentioned above, as described in FR-A-No. 2 347 306, cannot, in practice, be used industrially, as it involves a high risk that some of the steam which is applied during pressing of the material will condense on the material, giving rise to blemishes.